To the extent that large contributions are given to secure a political quid pro quo from current and potential office holders, the integrity of our system of representative democracy is undermined. Although the scope of such pernicious practices can never be reliably ascertained, the deeply disturbing examples surfacing after the 1972 election demonstrate that the problem is not an illusory one.

Buckley v. Valeo, 424 U.S 1, 27.

This was the magnitude of the conclusion that the Supreme Court drew about the prevalence or appearance of corruption when it upheld the contribution limitations of the Federal Election Campaign Act. The corruption problem was “not… illusory” but its scope could ‘never’ be pinned down. The Court then cited to the decision of the court below that had offered a few example of pernicious behavior with campaign funds in the 1972 presidential election. That was enough.

In the years following, enough has not proven to be as good as a feast. And in search of the feast, anyone with a point to make about the campaign finance laws has been pursuing conclusive data to support it. Corruption, or the absence of corruption, or the different definitions and measures of corruption, have all occasioned argument about the evidence, as has the related but different project of proving the “appearance” of corruption. Argument about the evidence has yet to be settled and there’s every reason to believe that they never will be.

The related but still distinguishable argument about political inequality has meant the same search for clinching proof that policy follows money and makes for a “rigged” system. This week, the Center for Competitive Politics took after a widely reported paper about the correlation between the aspirations of the wealthy and the manufacture of public policy. Noting that Rick Hasen and Larry Lessig had made use of the paper in arguing for a political equality theory of regulation, the CCP cited to critics of the scholarship and its conclusions. In this critical view, which CCP evidently favors, there is substantial agreement across income groups about policy. So the study that purportedly shows that we have a democracy of the rich cannot survive close scrutiny. CCP suggests that this should bring sharply into question the “lofty solutions” of reformers.

This fight holds unfortunate temptations for both sides. The advocates for more regulation want considerably more, and more aggressive, rules, and with the Congress in hostile hands and, until recently, a majority the Court having been unsympathetic, they can be drawn to improve their prospects with dramatic evidence. Studies of interest but not fully conclusive or persuasive come to be promoted with a surplus of zeal: the marketing can go a little far, outpacing the strength of the product. Along with this appetite for “smoking gun” evidence is a taste for the anecdotal, usually the contemporary “scandal” that is supposed to prove their point.

But the adversaries of regulation have their own irresistible impulses: to get carried away in their rebuttals. That a particular evidentiary claim is overstated is a point fairly made against overstatement. It does not justify overlooking or dismissing what is left of substance in the claim. Often this rejection of the evidence is rooted in ideology, which requires flat-out resistance to the reform project and a refusal to acknowledge any value in the data.

All this is enough to create the conditions for chronic disagreement in a cycle of unproductive exchanges. Add a sometimes open, sometimes concealed, difference over what the state is really after when regulating—permissibly preventing corruption or impermissibly “leveling the playing field”—and all hope for this discussion is largely lost.

The Buckley Court was deciding its case in the aftermath of national political crisis and comfortable taking certain points for granted. It did not pay much attention to the “record” below. It took it to be sufficiently clear, if not obvious, that some contributors some of the time give money to get results, that some of the time they may find a buyer, and that the potential for this, and the occasions on which it might happen, are dangerous to a democracy. These observations seem unexceptionable. There is a decent amount of evidence and experience, buttressed by common sense, to support regulation, such as contribution limits and disclosure requirements.

On the strength of this rationale, taking it as far as it can be plausibly taken and no farther, legislators could be expected to enact reasonable, carefully drawn rules. They would not have grounds for giving the most ardent proponents of regulation what they are pressing for, or for repudiating all or most controls, as the opponents of regulation would urge. Good evidence can help guide the decision, but it will not be put to good use if over-argued in order to push the choice too far in either direction. The McConnell decision is an example of a case that approved a marked shift toward regulation on a highly controversial record, and it shows that overreliance on contested, complex evidence can inflame disagreement rather than help end or temper it.

This is a challenge for the proponents of a political equality theory of regulation. But their position does not have to rely centrally on contested arguments about evidence. In his recent book, Plutocrats United (2016), Rick Hasen freely concedes the “unpredictable nature of the effect of money on both elections and policy.” (p.70). He then constructs his argument for rough political equality in campaign finance from an appeal to “modern democratic norms of equal representation,” (p. 65), aligning this cause with others in the past in which equality was at stake: the elimination of the poll tax, and the institution of the “one person, one vote” requirement. He asks whether “wealthy people and entitles [should have] a much greater chance of influencing electoral and policy outcomes than ordinary voters,” a question he takes to be urgent in “an age of rising inequality.” (pp. 65, 83).

This is essentially an argument that whatever may be the influence of wealth on politics, and accepting that its extent will never be reliably established, the problem, to quote the Buckley Court, “is not an illusory one.”